JPH09180902A - Semi-fixed resistor - Google Patents

Abstract

(57) Abstract: The present invention provides a semi-fixed resistor capable of improving connection reliability with a printed wiring board. SOLUTION: A terminal electrode 3 connected to both ends of a resistor film 2
a and 3b are semi-fixed resistors formed on one end surface side of the insulating substrate 1, and the conductive structure between the resistor film 2 and the terminal electrodes 3a and 3b is arranged below the end portion of the resistor film 2. Through the conductor through hole 12, it is connected to the back side conductor film 32 of the terminal electrodes 3a, 3b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semi-fixed resistor, and more particularly to a semi-fixed resistor which has high joint reliability when soldered onto a printed wiring board.

[0002]

2. Description of the Related Art A conventional semi-fixed resistor includes an insulating substrate 71, a horseshoe-shaped resistor film 72 on the insulating substrate 71, and a resistor film 72 on the insulating substrate 71, as shown in FIGS. A sliding body 73 having a sliding element 74 for sliding, and a caulking member 75 including a pin portion 75a and a terminal portion 75b for rotatably holding the sliding body 73 on the insulating substrate 71. ing.

A horseshoe-shaped resistor film 72 is formed on the insulating substrate 71, and both ends of the resistor film 72 are two terminal electrodes 72a formed on one end of the insulating substrate 71.
It is connected to 72b. These two terminal electrodes 72a,
The conductors 72b are formed by depositing a conductor film on the front surface, the rear surface and the end surface of the one end side end portion of the insulating substrate 71, and the end portion of the resistor film 72 is superposed on the conductor film on the front surface.

Further, a slider 7 sliding on the resistor film 72.
The sliding body 73 having 4 is rotatably held by a caulking member 75. A driver groove 76 is formed on the upper surface of the sliding body 73 so as to receive an external turning imparting force.

The above-mentioned semi-fixed resistor has a terminal electrode 72a,
72b and the terminal portion 75b are soldered to predetermined electrode pads formed on the printed wiring board, respectively, and the sliding body 73 is rotated by a driver or the like in a circuit in the printed wiring board, so that the resistor film 72 is formed. The relative position of the slider 74 to the terminal electrode 7 on one end side of the resistor film 72 is different.
A resistance value is obtained between 2a, the terminal portion 75b of the sliding member 73, and the terminal electrode 72b on the other end side of the resistor film 72 and the terminal portion 75b of the sliding member 73.

[0006]

In the above-described semi-fixed resistor, the terminal electrodes 72a and 72b need to be printed and baked with conductive paste on the three surfaces of the one end of the insulating substrate 71, respectively. .

In particular, the ridge line portion between the front surface side conductor film and the end surface side conductor film and the back surface side conductor film and the end surface side conductor film are not as smooth as the conductor paste when printing the conductive paste, and therefore are compared with the flat surface portion. As a result, the film thickness of the conductor film becomes very thin.

In such a state, when soldering is performed to a predetermined wiring pattern of the printed wiring board, the conductor film is eroded, resulting in the conductor film being divided.
There is a problem in that stable resistance film 72 and the terminal electrodes 72a and 72b cannot be electrically connected and stable resistance value characteristics cannot be obtained. For example, in the case of a solder jet, since the solder is jetted from the front surface side of the insulating substrate 71, disconnection is likely to occur at the ridge portion between the front surface side conductor film and the end surface side conductor film, and in the case of reflow solder bonding. Is likely to be subject to thermal shock on the ridgeline between the back surface side conductor film and the end surface side conductor film,
Division is likely to occur at this portion.

Further, in the semi-fixed resistor, if the resistance value width (resistance value variable range) that can be varied by one rotation is widened, the resistance value can be finely adjusted, and the insulating substrate 71 can be downsized. However, conventionally, the horseshoe-shaped resistor film 72 is formed in the range of about 260 to 270 °. That is, the opening between both ends of the horseshoe-shaped resistor film 72 was present with a width corresponding to 100 to 90 °. This is because conventionally, both ends of the resistor film 72 have terminal electrodes 72a,
Since it is superposed and connected to the front surface side conductor film of 72b, both patterns are provided with a margin so that stable superposed connection can be achieved even in consideration of the printing deviation of the front surface side conductor film and the resistor film 72. is there.

Therefore, the control of the variable range of the resistance value is performed by controlling the length of the resistor film 72 by changing the diameter of the resistor film 72.

It was dealt with by.

In such a measure, the diameter of the resistor film 72 influences the shape of the insulating substrate 71, and in particular, it is difficult to easily achieve a semi-fixed resistor having a small size and a wide resistance variable range. There was a problem.

The present invention has been devised in view of the above-mentioned problems, and an object thereof is to provide a semi-fixed resistor capable of obtaining stable bonding reliability even when soldered to a printed wiring board. To do.

Another object of the present invention is to provide a semi-fixed resistor which can easily form a resistor film whose resistance value variable range can be widened.

Still another object is to provide a semi-fixed resistor whose manufacturing method is simple.

[0016]

A first invention is a horseshoe-shaped resistor film formed on an upper surface of an insulating substrate, a slider sliding on the resistor film, and an end of the resistor film. And conducts
A semi-fixed resistor comprising a terminal electrode formed at one end of the insulating substrate and a terminal portion connected to the slider and arranged at the other end of the insulating substrate, The insulating substrate has a conductor through hole penetrating in the thickness direction of the insulating substrate at a position where the end of the horseshoe-shaped resistor film is formed, and the conductor through hole forms the end of the resistor film and the end of the resistor film. The semi-fixed resistor is electrically connected to the terminal electrode.

A second aspect of the invention is the semi-fixed resistor described above, wherein the end face portion of the terminal electrode is recessed from the end face of the insulating substrate.

[0018]

In general, although electrical connection and mechanical joining between the predetermined wiring pattern of the printed wiring board and the semi-fixed resistor are achieved by soldering between the terminal electrodes,
In particular, the mechanical joining is performed by the back surface side conductor film of the terminal electrode, and the solder is formed in the corner portion formed by the end surface conductor film and the wiring pattern, and becomes strong (solder fillet).

In the first aspect of the present invention, electrical continuity between the resistor film and the terminal electrode is achieved by a conductor through hole that conducts at the end of the resistor film from its lower portion to the back-side conductor film of the terminal electrode. ing. Therefore, the film thickness of the ridge line portion between the back-side conductor film and the end-face side conductor film of the terminal electrode becomes thin, and the ridge line portion is separated by the solder scuffing or thermal shock at the time of solder joining (solder jet or reflow joining). Even if
Substantial conduction between the resistor film and the terminal electrode can be stably maintained by the conductor through hole arranged inside the insulating substrate.

Further, since conduction between the resistor film and the terminal electrode is achieved by conductor through-hole conduction, in the structure in which the surface side conductor film of the terminal electrode for conducting the resistor film and the terminal electrode is essential. Disappear. That is, even if the surface side conductor film is omitted,
The end portion of the resistor film overlaps with the conductor through hole and the land portion formed by the formation of the conductor through hole, and conduction between the resistor film and the terminal electrode is achieved.

Therefore, by omitting the surface side conductor film of the conventional terminal electrode, the distance between both ends of the horseshoe-shaped resistor film can be made extremely close. For example, the horseshoe-shaped resistor film can be set to about 300 to 330 °, and the resistance value variable range is increased by 10% as compared with the conventional horseshoe-shaped resistor film having the same diameter. be able to. If the variable ranges are the same, on the contrary, it becomes easy to control a minute change and the area occupied by the resistor film can be reduced, so that a small semi-fixed resistor can be achieved.

In the second invention, the end surface side conductor film of the terminal electrode is formed at a position recessed from the end surface of the insulating substrate. This is very useful when the insulating substrate to be each element is divided by the dividing groove and is manufactured on a large substrate capable of extracting a plurality of elements. That is, if a through hole for forming a terminal electrode is formed so as to straddle an adjacent insulating substrate in the dividing groove on one side of the insulating substrate in the dividing groove of the large-sized substrate, In the step of forming the holes, the end face conductor film of the terminal electrode can be collectively formed, and the step of independently forming the end face conductor film can be omitted.

Further, structurally, since a part of the end face side conductor film of the terminal electrode on which the solder fillet is formed is recessed from the end face of the insulating substrate, the forming distance of the solder fillet increases and the solder fillet becomes stronger. Bonding with the printed wiring board can be achieved.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION A semi-fixed resistor according to the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a top view of a semi-fixed resistor according to the present invention, FIG. 2 is a plan view of an insulating substrate portion, and FIG. 3 is FIG.
FIG.

The semi-fixed resistor of the present invention comprises an insulating substrate 1 and
A resistor film 2 formed on the insulating substrate 1, terminal electrodes 3a and 3b connected to the resistor film 2, a slide body 4 including a contact sliding on the resistor film 2, and a slide body. The moving body 4 is rotatably held on the insulating substrate 1, and is composed of a caulking member 6 having a terminal portion 5 electrically connected to the sliding body 4.

The insulating substrate 1 is made of alumina ceramic or the like, and as shown in FIG. 2, a through hole 11 through which the caulking member 6 penetrates is formed in the center thereof.

A horseshoe-shaped resistor film 2 is formed around the through hole 11 on the insulating substrate 1 so as to coincide with the sliding direction of the contacts of the sliding body 4. The resistor film 2 is formed by printing, drying and baking a resistor paste such as ruthenium oxide.

Terminal electrodes 3a and 3b are formed on one end of the insulating substrate 1. This terminal electrode 3a, 3
b is on one end side of the insulating substrate 1, and is formed on, for example, two surfaces, an end surface and a back surface. The terminal electrode formed on the end face side is called the end face side conductor film 31, and the terminal electrode formed on the back face side is called the back face side conductor film 32.

Further, a through-hole having a conductor film formed so as to penetrate through the thickness of the insulating substrate 1 at the end portion of the resistor film 2 near one end of the insulating substrate 1 (hereinafter referred to as the conductor film, “Conductor through hole 12”) is formed.

In addition, in the end face on one end side of the insulating substrate 1, for example, in the portion where the end face side conductor film 31 of the terminal electrodes 3a, 3b is formed, a concave portion 13 recessed one step from the end face of the insulating substrate 1 is formed.
Are formed. An end surface side conductor film 31 is formed on the inner wall surface of the recess 13.

The terminal electrodes 3a and 3b are formed by printing, drying and baking a conductive paste containing Ag-based (Ag alone or Ag alloy such as Ag-Pd) as a main component. The terminal electrodes 3a and 3b are electrically connected to both ends of the resistor film 2 through the conductor through holes 12.

The sliding member 4 is made of stainless steel or the like and is formed, for example, in a dish shape as a whole, and a through hole through which the caulking member 6 penetrates is formed in the central portion thereof, and a driver groove is formed on the dish surface. 42 are formed respectively. Further, at least a part of the outer peripheral portion of the sliding body 4 is formed with a contact that slides on the resistor film 2.

The caulking member 6 is made of stainless steel, nickel silver, or the like, and the tip thereof is disposed in the dish-shaped sliding body 4 and caulked. The other tip extends to the other end of the insulating substrate 1 through the bottom surface of the insulating substrate 1 to form a terminal portion 5.

In the semi-fixed resistor having the above structure, when the sliding body 4 is rotated by a predetermined amount by an external rotation imparting member such as a driver, the contact position between the sliding body 4 and the resistor film 2 changes. , A predetermined resistance component is obtained between the terminal portion 5 electrically connected to the sliding body 4 and either or both of the terminal electrodes 3a and 3b electrically connected to the end portion of the resistor film 2. become.

A characteristic of the present invention is that the conduction between the resistor film 2 and the terminal electrodes 3a, 3b is performed by the conductor through hole 12 penetrating the thickness of the insulating substrate 1 below the end portion of the resistor film 2. That is what is being said.

Further, the end face side conductor film 31 of the terminal electrodes 3a, 3b is formed in the recess 13 recessed from the end face of the insulating substrate 1.

When such a semi-fixed resistor is surface-mounted on a predetermined wiring pattern of a printed wiring board by soldering, the predetermined wiring pattern and the terminal electrodes 3a, 3b.
An electric connection and a mechanical joint are achieved by interposing a solder between and. Especially, the mechanical joining is performed by the terminal electrode 3
The strength is improved by forming the solder fillet that rises at the right angle portion formed by the end surface side conductor film 31 of a and 3b and the wiring pattern. That is, the electrical connection with the predetermined wiring pattern is mainly performed on the back surface side conductor film 32 of the terminal electrodes 3a and 3b.
And a predetermined wiring pattern, mechanical joining,
It can be said that this is mainly performed between the end surface side conductor film 31 of the terminal electrodes 3a and 3b and the predetermined wiring pattern.

At this time, since the end face side conductor film 31 of the terminal electrodes 3a, 3b is directly exposed to the outside, the thermal shock during soldering becomes excessive, and particularly the end face side where the conductor film thickness becomes thin. Separation may occur at the ridgeline portion between the conductor film 31 and the back conductor film 32. However, in the above-described embodiment, the electrical continuity between the end portion of the resistor film 2 and the terminal electrodes 3a and 3b is provided inside the insulating substrate 1, specifically, the insulating substrate formed below the end portion of the resistor film 2. Since the conductor through-hole 12 penetrates through No. 1 in the thickness direction, an excessive thermal shock is not given. The conductor film is not divided at the ridge portion between the back surface side conductor film 31 and the conductor through hole 12, and stable electrical continuity between the resistor film 2 and the back surface side conductor film 31 of the terminal electrodes 3a and 3b is maintained. Will be done.

Therefore, as in the prior art, the conduction between the resistor film 72 and the back-side conductor films of the terminal electrodes 72a and 72b is such that the end portion of the resistor film 72-the front-side conductor film of the terminal electrodes 72a and 72b-the end surface. In the conductive structure between the side conductor film and the back face side conductor film, the conductor film is divided at the ridge line portion between the front face side conductor film and the end face side conductor film of the terminal electrodes 72a and 72b and between the end face side conductor film and the back face side conductor film. There is no need for stable characteristics to be obtained.

Further, in the present invention, if the terminal electrode 3
Even if the conductor film is divided at the ridge portion between the end surface side conductor film 31 and the back surface side conductor film 32 of a and 3b, the stable characteristics can be maintained as described above. Since the end face side conductor film 31 of the terminal electrodes 3a and 3b exists even if the film is divided, a strong mechanical joint can be achieved by the solder fillet generated in this portion.

In addition, the surface shape of the insulating substrate 1 shown in FIGS. 2 and 3, particularly the conduction between the resistor film 2 and the terminal electrodes 3a and 3b, contributes to an electrical connection through the conductor through hole 12. Since the back surface side conductor film 32 of the electrodes 3a and 3b is directly conducted, it is not necessary to form the front surface side conductor film of the terminal electrodes 3a and 3b as in the prior art. Therefore, the opening width of both ends of the horseshoe-shaped resistor film 2 can be narrowed to such an extent that both ends of the resistor film 2 are overlapped with the conductor through holes 12. For example, in the case of the conventional semi-fixed resistor, the opening widths at both ends of the resistor film 2 are set in consideration of the print displacement of the surface side conductor films of the terminal electrodes 72a and 72b and the print displacement of the resistor film 2. It is necessary to open it sufficiently, for example, it is necessary to open the horseshoe-shaped resistor film about 260 to 270 degrees, that is, to open the opening by an amount equivalent to 100 to 90 degrees. However, in the present invention, the horseshoe shape is up to about 300 degrees. Can be formed,
The openings at both ends can be made as narrow as about 60 °.

By narrowing the opening of the horseshoe-shaped resistor film 2 in this manner, the length of the resistor film 2 can be increased by about 10% or more in the horseshoe-shaped resistor film 2 having the same diameter. Therefore, the variable resistance value range can be widened in proportion thereto. Further, when the variable resistance value range is fixed, the area occupied by the resistor film 2 can be reduced, so that the semi-fixed resistor can be formed by the small insulating substrate 1. If the resistor material is selected so that the diameter of the resistance film 2 and the variable range of the resistance value are constant, the resistance value can be easily controlled to a minute value.

In the above-mentioned embodiment, in order to obtain the above-mentioned effects, the state in which the surface side conductor films of the terminal electrodes 3a and 3b are omitted is shown, but the widening of the resistance variable range is ignored. Then, the surface side conductor film of the terminal electrodes 3a and 3b may be formed as in the conventional case.

Further, in the semi-fixed resistor of the present invention, the end surface side conductor film 31 of the terminal electrodes 3a and 3b is formed on the inner wall of the recess 13 which is recessed from the end surface of the one end of the insulating substrate 1.

This is to firmly and mechanically join the printed wiring board and to simplify the manufacturing process.

First, regarding solid mechanical joining on the printed wiring board, as described above, although it is achieved by the solder fillet, the terminal electrodes 3a, 3a having a simple planar shape are used.
As compared with the end surface side conductor film 31 of b, the end surface side conductor film 31 in the concave portion 13 whose surface is recessed has a longer length in which the solder fillet is formed. For example, assuming that the shape of the recess 13 is a semicircular shape having a diameter a, the length thereof may be increased by about 1 / 2π times as compared with the end surface side conductor film of the planar terminal electrodes 3a and 3b. You can do it.

The reason for the simplification of the manufacturing method is that it is not necessary to form the end face side conductor film 31 of the terminal electrodes 3a and 3b independently.

4 to 5 are plan views showing a method for manufacturing a semi-fixed resistor according to the present invention.

In FIG. 4, a large substrate 100 from which a plurality of insulating substrates 1 can be extracted is used for manufacturing.

The large-sized substrate is formed with dividing grooves 101, 102 which divide into regions for each one element, and several through holes are formed to penetrate the thickness of the large-sized substrate 100 in accordance with the shape of the insulating substrate 1. There is. Particularly important through holes are the through hole 120 that becomes the conductor through hole 12 and the through hole 130 in which the end surface side conductor film 31 that becomes the terminal electrodes 3a and 3b is formed.

Through hole 120 to be the conductor through hole 12
Is formed at the position where the resistor film 2 of each element region is formed and becomes the end thereof. Also, the terminal electrodes 3a, 3b
The through hole 130 in which the end surface side conductor film 31 is formed is
It is formed so as to straddle the dividing groove 101 that divides one end side of each element.

Next, the terminal electrodes 3 are formed by printing a conductive paste from the surface side of each element region of the large-sized substrate 100.
The conductor film 131 serving as the end face side conductor film 31 of a and 3b is formed on the inner wall surface of the through hole 130, and the conductor through hole 12 is formed on the through hole 1.
20 and is baked. Subsequently, similar processing is performed from the back surface side of each element region of the large-sized substrate.

The printing process from the front surface side and the printing process from the back surface side may be interchanged, or the printing may be performed simultaneously.

Next, as shown in FIG. 5, the conductor through hole 12 is covered on the surface of each element region of the large-sized substrate.
By printing the resistance paste, the horseshoe-shaped resistor film 2 is printed and baked.

Next, the slide body 4 is slidably integrated with the through hole at the center of each element region by the caulking portion member 6 having the terminal portion 5, and each element region is divided along the dividing groove. To do.

As described above, since the end surface side conductor film 31 of the terminal electrodes 3a, 3b is formed by attaching the conductor film 131 to the inner wall of the through hole 130, that is, by printing on the front surface side and the back surface side. , Its manufacturing method becomes very simple.

When a conductive film to be the flat terminal electrodes 72a and 72b is formed on one end surface of the insulating substrate 71 as in the conventional case, at least two elements where both end surfaces of the insulating substrate 71 are exposed are provided. Although it was necessary to use strip-shaped substrates arranged in parallel, the present invention can use a large-sized substrate 100 in which a plurality of elements are arranged vertically and horizontally.

Regarding the disposition of the slide body 4, the large-sized substrate 10 before being divided along the dividing grooves 101 and 102 is processed.
It can be carried out in the state of 0, which also makes the manufacturing method very simple.

In the present invention, the terminal electrodes 3a, 3b.
Although the front surface side conductor film can be eliminated, the resistance film 2 and the back surface side conductor film 32 can be electrically connected to each other through the conductor through hole 12 and the front surface side conductor film (not shown) -the end surface side conductor film 31-.
The conduction of the back side conductor film 32 may be used together.

Also, although it has a three-terminal semi-fixed resistor, that is, the terminal electrodes 3a and 3b and the terminal portion 5, it is a two-terminal semi-fixed resistor, that is, one end of the resistor film 2. It may be a semi-fixed resistor having the side terminal electrode 32a or 32b and the terminal portion 5.

Further, the through hole 12 of the conductor through hole 12
The shape of 0 can be exemplified by an elliptical shape, a rectangular shape, etc. in addition to the circular shape, and this through hole 120 has a shape that is equal to or slightly smaller than the width of the resistor film 2 in the variable resistance value range. Is desirable for widespread use. For example, the diameter of the circular through hole may be 0.3 to 1.5 mm.

Further, the shape of the recess 13 in which the end surface side conductor film 31 of the terminal electrodes 3a, 3b is formed is a semi-circular shape as long as the opening appears on the end surface on one side of the insulating substrate 1. In addition, any shape such as a semi-elliptical shape and a rectangular shape may be used.
It may have a shape such as four circles.

Further, the through hole 120 and the terminal electrodes 3a, 3b.
When the conductive paste is adhered to each inner wall of the recess 13 which becomes the end surface side conductor film 31, the conductive paste is easily controlled by its own weight by controlling the viscosity of the conductive paste and by the depressurizing process from the side opposite to the printing surface. It can be attached.

The end surface side conductor film of the terminal electrodes 3a and 3b may be printed at least only on the back surface side of the insulating substrate 1.

Further, when the opening between both ends of the resistor film 2 is narrowed, in order to prevent the both ends from being short-circuited due to the sagging of the resistance paste or the like, at least the resistor is provided in the opening between both ends. A recess having a depth equal to or larger than the thickness of the film 2 may be formed from one end of the insulating substrate 1 toward the through hole 11.

[0067]

As described above, according to the present invention, conduction between the resistor film and the terminal electrode is achieved by the conductor through hole penetrating the thickness of the insulating substrate inside the insulating substrate. Even if the conductor film is divided at the ridge portion between the end face side conductor film and the back face side conductor film where the conductor film becomes thinner, stable resistance characteristics can be derived.

Further, since the surface side conductor film of the terminal electrode can be omitted, the shape of the resistor film, especially the opening of the horseshoe-shaped resistor film can be narrowed, so that the substantial resistor film can be formed. Since the length can be increased, the variable range of the resistance value can be widened.

Furthermore, the conductor film portion on the end face side of the terminal electrode is
Since it is formed to be recessed from the end surface of the insulating substrate, the bonding strength to the printed wiring board can be improved, and the other conductor film is formed by printing the conductor film on the front surface side and / or the back surface side. Therefore, the manufacturing method is simplified.

[Brief description of the drawings]

FIG. 1 is a plan view of a semi-fixed resistor of the present invention.

FIG. 2 is a plan view of an insulating substrate portion.

FIG. 3 is a sectional view taken along line XX of FIG.

FIG. 4 is a plan view of a large substrate used for manufacturing the semi-fixed resistor of the present invention.

FIG. 5 is a plan view showing a state in which a resistor film is formed in the method for manufacturing a semi-fixed resistor according to the present invention.

FIG. 6 is a plan view of a conventional semi-fixed resistor.

FIG. 7 is a sectional view of a conventional semi-fixed resistor.

[Explanation of symbols]

 1 ... Insulating substrate 11 ... Through hole 12 ... Conductor through hole 2 ... Resistor film 3a, 3b ... Terminal electrode 31 ... Recess 4 ... .... Sliding body 6 ...

Claims (2)

[Claims] 1. A horseshoe-shaped resistor film formed on an upper surface of an insulating substrate, a slider that slides on the resistor film, an end portion of the resistor film, and one of the insulating substrates. A semi-fixed resistor comprising a terminal electrode formed at a side end portion and a terminal portion connected to the slider and arranged at the other end portion of the insulating substrate, wherein the insulating substrate has a horseshoe shape. A conductor through hole penetrating in the thickness direction of the insulating substrate is formed at a position where the end of the resistor film is formed, and the end of the resistor film and the terminal electrode are electrically connected by the conductor through hole. Semi-fixed resistor characterized in that they are electrically connected. 2. The semi-fixed resistor according to claim 1, wherein the end face portion of the terminal electrode is recessed from the end face of the insulating substrate.